Controlling superconducting transistor by coherent light

Abstract: The Josephson junction is typically tuned by a magnetic field or electrostatic gates to realize a superconducting transistor, which manipulates the supercurrent in integrated superconducting circuits. However, this tunable method does not achieve simultaneous control for the supercurrent phase (phase difference between two superconductors) and magnitude. Here, we propose a novel scheme for the light-controlled superconducting transistor, which is composed of two superconductor leads linked by a coherent light-driven quantum dot. We discover a Josephson-like relation for supercurrent $I_{\mathrm{s}}=I_{c}(\Phi)\,\sin\Phi$, where both supercurrent phase $\Phi$ and magnitude $I_{c}$ could be entirely controlled by the phase, intensity, and detuning of the driving light. Additionally, the supercurrent magnitude displays a Fano profile with the increase of the driving light intensity, which is clearly understood by comparing the level splitting of the quantum dot under light driving and the superconducting gap. Moreover, when two such superconducting transistors form a loop, they make up a light-controlled superconducting quantum interference device (SQUID). Such a light-controlled SQUID could demonstrate the Josephson diode effect, and the optimized non-reciprocal efficiency achieves up to $54\%$, surpassing the maximum record reported in recent literature. Thus, our feasible scheme delivers a promising platform to perform diverse and flexible manipulations in superconducting circuits.